This invention relates to a method of manufacturing open top, walled members such as troughs, runners, ladles and other vessels-which are used for containing and processing molten iron and steel. It is well known in the art that such open, top walled members must have sufficient structural integrity to support a molten metal poured therein. This invention provides walled containment members that can be dried faster than conventionally-constructed containment members and which have fewer porosity problems and imperfections, especially at the tops of the walled containment members where the walls are in contact with slags contained in the molten iron and metal.
This invention is especially advantageous when the casting compound described in U.S. patent application No. 07/527,033, filed May 21, 1990, and assigned to the same assignee as this patent application, is used to form the walled containment members since the need for cranes and hoppers to transport the casting compound to the molds and the steel plates which make up the conventional inner walls of the molds are eliminated. The entire disclosure of said patent application is incorporated herein by reference.
Conventionally, troughs and runners for transporting molten iron and steel are constructed in situ near a tap spout of a blast furnace or other molten metal container. The mold for the trough or runner utilizes the existing walls of a trench or, other existing structure as the outer (lower) walls of the mold. The inner (upper) walls of such molds have conventionally been formed of heavy steel plates spaced from the outer walls leaving only an open space between the outer and inner mold walls in which to pour the casting compound and to provide a venting area for the release of moisture during setting of the casting compound. In the past, the drying process, which is necessary to properly cure the casting compound, could not be started until the casting compound had set sufficiently to allow removal of the heavy steel plates of the inner walls of the mold because of the limited venting area for the release of moisture during the drying of the casting compound, which venting area was provided around the top periphery of the mold between the inner and outer walls thereof. When the trough or runner is out of service, the furnace or molten metal container is out of service and each hour a furnace is out of service is costly.
In accordance with my invention, the inner mold walls which conventionally had been constructed of heavy steel plate are replaced with an open mesh, galvanized steel screen of the type which has been used in retaining poured concrete in conventional building construction. The removal of the open mesh screen by the introduction of molten metal after the casting compound has been completely dried is one distinguishing feature of my method in comparison with the use of similar mesh in concrete building construction where the mesh remains as a structural element of the completed concrete construction. In my method, the use of the open mesh screen as the inner walls of the mold permits the drying process for the casting compound to be started as soon as the pouring process ends. It is not necessary to wait for the casting compound to set because the mesh screen is not removed during the drying process. There are adequate openings in the mesh screen to permit venting of moisture from the drying compound and, in fact, the mesh screen is not removed until it is melted by the molten metal being introduced into the finished trough or runner. Also, since the mesh screen is lightweight and the casting compound is of a consistency that it can be pumped into the mold cavity, cranes and hoppers are not needed in the construction of the troughs and runners according to my method, thereby reducing the cost of such an installation.
My invention is also adaptable to the repair and reconstruction of worn troughs, runners, ladles and other vessels used for containing and processing molten iron and steel. Repair and reconstruction is accomplished by removing damaged refractory material, installing the open mesh screen as the inner walls of the mold and pouring in replacement casting compound. The replacement casting compound is pumped between the screen and the remaining original compound walls. As in the case of original installation, the drying process may be started immediately without waiting for the casting compound to set and the inner mold walls to be removed.